November 07, 2007

The universe is a very complex place; there’s no doubting that. It continually throws up new questions that scientists have to answer, or answers that we just don’t know the question for. One of these questions is where is all the mass?

To better understand what it is that is going on in this article let’s start off with University of Alabama in Huntsville’s own analogy;

Imagine “if billions of lights thought to come from billions of
aircraft carriers were found instead to come from billions of extremely
bright fireflies.”

This is the analogy that is framing the problem researchers from the
University of Alabama Huntsville are facing. The same group of
researchers that, back in 2002, announced to the world that they had
found a large fraction of the “missing mass” of our universe has,
essentially, retracted that statement.

Let’s explain.

The universe must be a certain mass to fit in to one of the three
expansion models proposed in the early 20th century. And, with all the
research that has been done, scientists have begun to get an idea of
just how heavy the universe is (and by heavy, I mean its mass). But
there is a difference between what we measure the universe to be, and
what we can observably weigh.

In other words, all of what we can see – the gas, dust, planets and
stars – don’t add up to the right mass to provide the answer “stable
universe.

So “where is all the missing matter?” is question that has been asked for a very long time.

Dark matter is one of those substances that, while unobservable, is
believed to add up to fit the “stable universe” equation. But the UAH
researchers, in 2002, found what they believed to be another
cohabitating answer; heavy x-rays.

Those x-rays allowed scientists to be a little safer in their answers.
But all of a sudden the same researchers have announced that, instead
of hefty atoms being expelled, the x-ray emitting clouds are emitting
tiny electrons.

"This means the mass of these x-ray emitting clouds is much less than
we initially thought it was," said Dr. Max Bonamente, an assistant
professor in UAH's Physics Department. "A significant portion of what
we thought was missing mass turns out to be these 'relativistic'
(travelling at the speed of light) electrons."

And though tiny electrons don’t seem to be all that heavy, the sheer
amount of them added up to 10% of the mass that is thought to hold the
universe together; keeping it from spinning out of control.

The most logical explanation seems to be that a large amount of the
energy comes from electrons that are smashing into other photons
instead of from warm atoms and ions, which would have recognizable
spectral emission lines. "We have never been able to detect spectral
emission lines associated with those detections," Bonamente explained.
"If this 'bump' in the data were due to cooler gas, it would have
emission lines."

But this latest discovery also exposes the problem that, the lighter
x-rays they have discovered, may have been “puffing up” the mass of
galaxy clusters in the past. Energy used from galaxy clusters – the
universes largest object – helped scientists calculate the mass. Now
that such energy is connected to light-weight electrons, those
measurements drop as well.

Results of this research by Bonamente, Jukka Nevalainen of
Finland'sHelsinki Observatory and UAH's Dr. Richard Lieu were published
Oct. 20 in the "Astrophysical Journal. So if you manage to get your
hands on it, make sure you contact me! I want to know more.